"Meetings are the time waster there is" vs. "There is a meeting which is the time waster"
"Meetings are the biggest time waster there is."

It is the sentence I want to understand.
I've never seen that 'there is' is put at the end of a sentence.
When I saw this sentence, I understood the meaning, but it was weird to me.

"Meetings are the biggest time waster there is" vs. "There is a meeting which is the biggest time waster"
Do they have the same meaning?
And why is 'there is' used in that way?

Thank you very much!!

Question

"Meetings are the time waster there is" vs. "There is a meeting which is the time waster"
"Meetings are the biggest time waster there is."

It is the sentence I want to understand. 
I've never seen that 'there is' is put at the end of a sentence. 
When I saw this sentence, I understood the meaning, but it was weird to me.

"Meetings are the biggest time waster there is" vs. "There is a meeting which is the biggest time waster"
Do they have the same meaning?
And why is 'there is' used in that way?

Thank you very much!!

Answer

No, the meanings are not the same.

In this context, "meetings" ("meeting" in the plural with the zero article) indicates a general category.

"Meetings are the biggest time waster there is."
=
"Meetings AS A CATEGORY are the biggest time waster there is."
=
"Meetings as a category are the biggest time waster THAT there is."
=
"Meetings as a category are the biggest time waster THAT EXISTS."

Answer

Thank you so much!! :)

Answer

They don’t have the same meaning, no.
“Meetings are the biggest time waster there is”
This means meetings are the biggest waste time, in a general sense.
“There is a meeting which is the biggest time waster”

This means there is a specific meeting which is the biggest time waste..

“There is” is required because “biggest” is a superlative adjective. It compares meetings in general with everything else (in the world)